A Minimally Invasive and Highly Effective Extracorporeal CO2Removal Device Combined with a Continuous Renal Replacement Therapy

OBJECTIVES: Extracorporeal carbon dioxide removal is used to treat patients suffering from acute respiratory failure. However, the procedure is hampered by the high blood flow required to achieve a significant CO2clearance. We aimed to develop an ultralow blood flow device to effectively remove CO2combined with continuous renal replacement therapy (CRRT). DESIGN: Preclinical, proof-of-concept study. SETTING: An extracorporeal circuit where 200 mL/min of blood flowed through a hemofilter connected to a closed-loop dialysate circuit. An ion-exchange resin acidified the dialysate upstream, a membrane lung to increase Pco2and promote CO2removal. PATIENTS: Six, 38.7 ± 2.0-kg female pigs. INTERVENTIONS: Different levels of acidification were tested (from 0 to 5 mEq/min). Two l/hr of postdilution CRRT were performed continuously. The respiratory rate was modified at each step to maintain arterial Pco2at 50 mm Hg. MEASUREMENTS AND MAIN RESULTS: Increasing acidification enhanced CO2removal efficiency of the membrane lung from 30 ± 5 (0 mEq/min) up to 145 ± 8 mL/min (5 mEq/min), with a 483% increase, representing the 73% ± 7% of the total body CO2production. Minute ventilation decreased accordingly from 6.5 ± 0.7 to 1.7 ± 0.5 L/min. No major side effects occurred, except for transient tachycardia episodes. As expected from the alveolar gas equation, the natural lung Pao2dropped at increasing acidification steps, given the high dissociation between the oxygenation and CO2removal capability of the device, thus Pao2decreased. CONCLUSIONS: This new extracorporeal ion-exchange resin-based multiple-organ support device proved extremely high efficiency in CO2removal and continuous renal support in a preclinical setting. Further studies are required before clinical implementation.